1. Field of the Invention
The present invention relates to a slip suppression control system for a vehicle which is configured to control a wheel driving power according to a wheel traction state on a road surface.
2. Description of the Related Art
Conventionally, there is proposed a traction controller configured to reduce an engine driving power to restore a drive wheel traction on a road surface (e.g., see Japanese Laid-Open Patent Application Publication No. Hei 7-103009). This controller uses traction control for retarding an ignition timing of the engine with respect to an optimal timing to reduce the driving power if an increase rate of an engine speed exceeds a predetermined start threshold, thus inhibiting a slip.
When the state where the monitored value is larger than the threshold continues, the retard condition of the ignition timing is maintained to continue a reduced state of the driving power. Thus, drive wheel traction on the road surface is restored and a slip is eliminated. However, if the monitored value exceeds the threshold significantly, a slip of the drive wheel on the road surface is not easily suppressed by maintaining the retard condition of the ignition timing. As a result, the reduced state of the driving power continues for a long time.